The PBGC applies the rules in subpart D of part 4000 of this chapter to compute any time period under this part. However, for purposes of determining the amount of a late payment interest charge under § 4007.7 or of a late payment penalty charge under § 4007.8 , the rule in § 4000.43(a) of this chapter governing periods ending on weekends or Federal holidays does not apply.
29 C.F.R. §4007.6